No princípio... Kaput cosmologia???

sexta-feira, janeiro 01, 2016

In the beginning

Cosmology has been on a long, hot streak, racking up one imaginative and scientific triumph after another. Is it over?

Source/Fonte: Aeon

by Ross Andersen

Ross Andersen is a senior editor at The Atlantic where he oversees the Science, Health and Technology sections. He was formerly the deputy editor of Aeon.

9,500 words

Edited by Brigid Hains

One crisp day last March, Harvard professor John Kovac walked out of his office and into a taxicab that whisked him across town, to a building on the edge of the MIT campus. People were paying attention to Kovac’s comings and goings that week. He was the subject of a fast-spreading rumour. Kovac is an experimental cosmologist midway through the prime of a charmed career. He did his doctoral work at the University of Chicago and a postdoc at Caltech before landing a professorship at Harvard. He is a blue chip. And since 2009, he has been principal investigator of BICEP2, an ingenious scientific experiment at the South Pole.

Kovac had come to MIT to visit Alan Guth, a world-renowned theoretical cosmologist, who made his name more than 30 years ago when he devised the theory of inflation. Guth told Kovac to take the back steps up to his office, to avoid being seen. If Guth’s colleagues caught a glimpse of the two men talking, the whispers swirling around Kovac would have swelled to a roar.

The science of cosmology has achieved wonders in recent centuries. It has enlarged the world we can see and think about by ontological orders of magnitude. Cosmology wrenched the Earth from the centre of the Universe, and heaved it, like a discus, into its whirling orbit around one unremarkable star among the billions that speed around the black-hole centre of our galaxy, a galaxy that floats in deep space with billions of others, all of them colliding and combining, before they fly apart from each other for all eternity. Art, literature, religion and philosophy ignore cosmology at their peril.

But cosmology’s hot streak has stalled. Cosmologists have looked deep into time, almost all the way back to the Big Bang itself, but they don’t know what came before it. They don’t know whether the Big Bang was the beginning, or merely one of many beginnings. Something entirely unimaginable might have preceded it. Cosmologists don’t know if the world we see around us is spatially infinite, or if there are other kinds of worlds beyond our horizon, or in other dimensions. And then the big mystery, the one that keeps the priests and the physicists up at night: no cosmologist has a clue why there is something rather than nothing.

To solve these mysteries, cosmologists must make guesses about events that are absurdly remote from us. Guth’s theory of inflation is one such guess. It tells us that our Universe expanded, exponentially, a trillionth of a trillionth of a trillionth of a second after the Big Bang. In most models of this process, inflation’s expansive kick is eternal. It might cease in particular parts of the cosmos, as it did in our region, after only a fraction of a second, when inflation’s energy transformed into ordinary matter and radiation, which time would sculpt into galaxies. But somewhere outside our region, inflation continued, generating an infinite number of new regions, including those that are roaring into existence at this very moment.

Not all these regions are alike. Quantum mechanics puts a slot-machine spin on the cosmic conditions of every region, so that each has its own physical peculiarities. Some contain galaxies, stars, planets, and maybe even people. Others are entirely devoid of complex structures. Many are too alien to imagine. The slice of space and time we can see from Earth is 90 billion light years across. Today’s inflationary models tell us that this enormous expanse is only one small section of one tiny bubble that floats along in a frothy sea whose proportions defy comprehension. This vision of the world is wondrous, in its vastness and variety, in the sheer range of possibilities it suggests to the mind. But could it ever be proved?

John Kovac had come to MIT to deliver good news. In 2009, Kovac and colleagues installed a telescope at the bottom of the Earth, and with it caught some of the oldest light in the Universe. He’d come to tell Guth that this light bore scars from time’s violent beginning, scars that strongly suggested the theory of inflation is true.

If the BICEP2 discovery held up, it would mint Nobel Prizes, and his would be the first

That same week, Chao-Lin Kuo, one of Kovac’s collaborators, paid a similar visit to Andrei Linde, another pioneer of inflationary theory. Kuo surprised Linde at his home, not far from Stanford’s sunny Silicon Valley campus. He brought a cameraman to record the moment for posterity, and a bottle of Champagne. When he knocked on Linde’s door, Linde and his wife answered. ‘I have a surprise for you,’ Kuo said. Linde’s wife, Renata Kallosh, who is also a physicist, was the first to react. She closed her eyes and hugged Kuo. Linde was stunned. ‘What?!’ he said, before asking Kuo to repeat the data. Soon, they were drinking Champagne, and Linde was effusive. ‘If this is true,’ he said, ‘this is a moment of understanding of nature of such magnitude, it just overwhelms.’

Back at MIT, Guth grilled Kovac with question after question, feeling around for weaknesses in the data. Guth would want to be sure. If the BICEP2 discovery held up, it would mint Nobel Prizes, and his would be the first. It would mean that an extraordinary idea entered human culture by way of his imagination. After more than an hour of interrogation, Guth relented. He could find no fault with the data.

A week later, the BICEP2 team went public, sparking a rare media event for the cerebral science of cosmology. In a front-page story for The New York Times Magazine, Kovac was quoted saying there was a one-in-10-million chance that the result was a fluke. The MIT physicist Max Tegmark told the Times that Kovac’s work would be one of the greatest discoveries in the history of science, ‘if [it] stays true’. For a time, it seemed as though cosmology had once again delivered a new cosmos.

When you read that word cosmos, you might begin to imagine the most expansive physical world your mind can build. Deep fields of glittering, star-filled galaxies stretching out in every direction, and maybe into forever. But even that image represents only the barest sliver of what is meant by ‘cosmos’. To build a cosmos, you have to extend your imagination to all of space and all of time. Only one of Earth’s creatures can pull off that cognitive trick. All living things are attuned to their environment: bacteria can sense chemical shifts in their immediate surroundings; migrating birds know our planet well enough to wing annually across its whole face; dung beetles navigate by the light of the Milky Way. But only the human being lives inside a cosmos, and only recently.

By the end of the last Ice Age, humans had travelled to every continent on Earth except Antarctica. At some point during these prehistoric wanderings, we began to pay close attention to the celestial realm. There are hints of this in Paleolithic cave art, where we find the first etchings of the Moon and its phases, its cycling from silver sliver to illuminated whole, and back again. We see it in the stone pillars that humans hauled across landscapes, to form rings that tracked the Sun’s seasonal arcs through the sky.

But these clues are few and far between. They aren’t enough for us to sketch the wider cosmos that the prehistoric mind inhabited. The first cosmos we can confidently describe comes down to us from the Bronze Age, whose belief systems were caught and preserved, in a newly invented cultural amber called writing. Even these, we know only crudely. Just well enough to identify a few of their common elements.

The ancient cosmos was not a complex mathematical structure. It was a sensory world, stitched together from people’s everyday experiences, people who had never seen Earth’s curves from orbit, or the night sky as magnified by a telescope. The ancient cosmos had a beginning, a birth out of a formless state, usually an infinite liquid realm, or a chaotic void that would suddenly separate into opposites, like light and darkness, or fire and ice, or earth and sky. This separation concept is still with us today in scientific creation stories, which often invoke a primordial splitting of symmetries. But the ancient versions were much more vivid. In the sacred Sanskrit text the Rig Veda, the universe begins as a symmetrical orb of pure potential, an egg surrounded by an infinite amniotic sea, which splits into two bowls of earth and sky, with the yolk-like sun hovering somewhere in the middle.

The earth that emerged from this primordial separation was usually a flat, round disc, wrinkled by mountains, cut through with rivers, and surrounded by ocean on every side. Above this disc was the closed dome of the sky, and below it was an underground realm of equivalent size. Together, they formed a sphere. Every night, the sun would travel through the invisible underworld after teetering over the horizon’s edge. The ancients knew this because the sun reappeared at dawn on the earth’s opposite side.

Read more here/Leia mais aqui: Aeon